Title: Simulation of Compound Flood Events in Low-Gradient Coastal Watersheds

Committee: M. Bilskie, S. Hagen, C. Willson, K. Konsoer

Degree/Institution:  Doctor of Philosophy from the Louisiana State University


Low-gradient coastal watersheds are susceptible to flooding caused by various flows such as rainfall, tides, and storm surge. Compound flooding occurs when at least two of these mechanisms happen simultaneously or in close succession. Different inundation models, observed data, and/or a combination of these are coupled through varying techniques involving one-way, loosely, tightly, or fully coupled approaches to assess compound flooding. This study presents a one-dimensional (1-D), fully coupled compound inundation model based on the Shallow Water equations. This model approach simultaneously simulates the free water surface variations in the ocean domain (i.e., tide and storm surge modeling), rainfall-runoff in the watershed’s upland region (i.e., hydrology modeling), and compound flooding within a defined coastal transition zone. To test this compound inundation model, various 1-D transects, representing idealized low-gradient coastal watersheds, were applied under various forcing conditions (rainfall-runoff/tides/storm surge combinations) that vary in magnitude, time, and space. These flooding scenarios include antecedent rainfall conditions in the watershed region and tropical cyclone-driven storm surge. This study’s primary goal is to evaluate each flooding mechanism and the associated hydrodynamic responses to aid in the identification of generalized coastal transition zones and enhance the production of flood maps for varying regions in the coastal watershed. The compound flood hazard zones’ migration will be evaluated for past, present, and future (c. 1890 – 2090) conditions of the Mississippi River Delta Plain using an existing two-dimensional (2-D) compound inundation model. The desire is a more holistic compound inundation model that can be a critical tool for decision-makers, stakeholders, and authorities who provide evacuation planning to save human lives and enhance resilience.

Publication Language: English

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